In a mobile communication system, a handover indicates a process which is performed for maintaining communication when a user equipment, for example, a mobile station moves between mobile communication areas, that is, from a base station area, in which communication is established, to another base station. In other words, the handover indicates an operation for performing the exchange of channels or lines so as to maintain a call. The handover may be performed in case where the status of a radio channel in a base station which is being used by a mobile station is bad, in a case where a mobile station moves from a current sector to another sector in a base station, or in a case where, when a mobile station moves from a current base station area to another base station area, the base stations are managed by the same mobile switching center (MSC) or different MSCs.
In order to perform a handover, a mobile station or a base station collects a downlink channel status, determines whether the handover is performed or not, and performs the handover regardless of uplink or downlink.